Conventionally, there have existed combined air-conditioning and hot water supply systems that are equipped with a refrigerant circuit formed by connecting a use unit (indoor unit) and a hot water supply unit (hot water supply device) to a heat source unit (outdoor unit) by pipes, thereby enabling an air-conditioning operation and a hot water supply operation to be executed at the same time (see, for example, Patent Literatures 1 to 3).
In these combined air-conditioning and hot water supply systems, conventionally, a plurality of use units (indoor units) are connected to a heat source unit (outdoor unit) via connecting pipes (refrigerant pipes), thereby allowing individual use units to execute a cooling operation or a heating operation. In addition, by connecting the hot water supply unit to a heat source side unit by connecting pipes (refrigerant pipes) or a cascade system, the hot water supply unit can perform hot water supply operation. That is, the air-conditioning operation of a use-side unit and the hot water supply operation of the hot water supply unit can be executed simultaneously. Also, in combined air-conditioning and hot water supply systems, hot water supply operation is executed in the hot water supply unit when cooling operation is being executed in the use unit. Therefore, waste heat generated in the cooling operation can be recovered, thereby achieving highly efficient operation.